fix misinitialized UNDEFINED attribute type; reordered members of AttributeType because I don't know a portable way to statically initialize a mutex :)

compile cleanly when BDB_FILTER_INDICES is defined, but I have not
yet seen whether any of it actually works. In particular, I don't
understand the "range" argument to the candidate functions...

non-root modrdn of entries rooted at '' checks children write permission (completes previous add/delete fix; needs be ported to back-bdb)

Forced SLAP_USE_AD code, removed ifdefs of old code. filterindex.c is
still badly broken when BDB_FILTER_INDICES is defined, working on that...

(will fix up back-bdb next.)

ad_find_lang() to search an AttributeType for a given language variant.
(Will be used in back-bdb/back-ldbm index code...)

non-root add/delete of entries rooted at '' checks children write permission (forward port from back-ldbm)

timelimit must be checked on first entry.

trival other cleanup.